Reactions of TcI(NO) and TcVN Complexes with Alkynes and Alkynides

• Published in: Organometallics 2022-08, Vol.41 (15), p.2011-2021
• Main Authors: Ernst, Moritz Johannes, Roca Jungfer, Maximilian, Abram, Ulrich
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.2c00192

An unprecedented trimeric complex of the composition [{Tc­(NO)­(PPh3)­(μ2-Cl)}3(μ3-O)­(μ3-Cl)] is formed during an attempted reaction of [TcI(NO)­Cl2(PPh3)2(CH3CN)] with PhCCPh in boiling toluene. No evidence for the intended formation of complexes with a side-on bonded alkyne was found during this reaction or with a variety of other technetium starting materials. Most of such reactions resulted in a recovery of the starting materials and/or in the isolation of unexpected side products. Reactions of the technetium­(V) complex [TcNCl2(PPh3)2] with lithium acetylides, however, give five-coordinate products of the composition [TcN­(CCR)2(PPh3)2] (R = t Bu, SiMe3, Ph­(CF3)2). The complexes are stable as solids but undergo a gradual decomposition in solutions. The choice of the solvents used for the synthesis and purification operations is crucial to obtain pure products in satisfactory yields. Similar results were also obtained for the corresponding rhenium complexes [ReN­(CCR)2(PPh3)2] with R = SiMe3 or Ph­(CF3)2, which have been used to optimize the reaction conditions for the Tc complexes.